Fenton, Mo., company was tasked with mitigating pollutants from closed mine. Missouri-based Environmental Restoration LLC was the contractor whose work caused a mine spill in Colorado that released an estimated 3 million gallons of toxic sludge into a major river system ... The EPA, which was overseeing the servicing of the mine, had previously said an unnamed outside contractor was using heavy equipment when it accidentally triggered a breach in the abandoned Gold King Mine, letting out wastewater that had built up inside it. āEnvironmental Restoration LLC was working at the direction at EPA ... Environmental Restoration is one of...